Re: [PATCH] perf evlist: Print hint for group

[Arnaldo Carvalho de Melo]

On Mon, Sep 09, 2024 at 09:54:57AM -0700, Ian Rogers wrote:
> On Sun, Sep 8, 2024 at 1:28 PM <kan.liang@xxxxxxxxxxxxxxx> wrote:
> >
> > From: Kan Liang <kan.liang@xxxxxxxxxxxxxxx>
> >
> > An event group is a critical relationship. There is a -g option that can
> > display the relationship. But it's hard for a user to know when should
> > this option be applied.
> >
> > If there is an event group in the perf record, print a hint to suggest
> > the user apply the -g to display the group information.
> >
> > With the patch,
> >
> >  $perf record -e "{cycles,instructions},instructions" sleep 1
> >  [ perf record: Woken up 1 times to write data ]
> >  [ perf record: Captured and wrote 0.024 MB perf.data (4 samples) ]
> >
> >  $perf evlist
> >  cycles
> >  instructions
> >  instructions
> >  # Tip: use 'perf evlist -g' to show group information
> >
> >  $perf evlist -g
> >  {cycles,instructions}
> >  instructions
> >
> > Suggested-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
> > Closes: https://lore.kernel.org/lkml/ZttgvduaKsVn1r4p@x1/
> > Signed-off-by: Kan Liang <kan.liang@xxxxxxxxxxxxxxx>
> 
> Reviewed-by: Ian Rogers <irogers@xxxxxxxxxx>

Thanks, tested:

    Committer testing:
    
    So for a perf.data file _with_ a group:
    
      root@number:~# perf evlist -g
      {cpu_core/branch-instructions/pp,cpu_core/branches/}
      dummy:u
      root@number:~# perf evlist
      cpu_core/branch-instructions/pp
      cpu_core/branches/
      dummy:u
      # Tip: use 'perf evlist -g' to show group information
      root@number:~#
    
    Then for something _without_ a group, no hint:
    
      root@number:~# perf record ls
      <SNIP>
      [ perf record: Woken up 1 times to write data ]
      [ perf record: Captured and wrote 0.035 MB perf.data (7 samples) ]
      root@number:~# perf evlist
      cpu_atom/cycles/P
      cpu_core/cycles/P
      dummy:u
      root@number:~#
    
    No suggestion, good.
    
    Suggested-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
    Reviewed-by: Ian Rogers <irogers@xxxxxxxxxx>
    Signed-off-by: Kan Liang <kan.liang@xxxxxxxxxxxxxxx>
    Tested-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>


Applied.

- Arnaldo